So, I finally got in my glue that John from Sci-Fire recommended. It is Weld-on #4807 Styrene Glue. You can get it here:
http://www.rplastics.com/weldon4807.html
This is a SOLVENT Cement which really holds the parts together incredibly well, but it does melt the plastics a bit, so be warned!
This is NOT a fast-setting glue and your pieces need to be fairly flat and match up fairly well... Most of all, make SURE you pieces are in the correct position because once this glue cures, there is no possible was of disjoining the pieces!
Because I cut so much material out of the biceps, they no longer created a circle but had a somewhat football shape with the joins being pointed.
I used a heat gun (be careful of the fumes!) to mold them into a more cylindrical shape, then added a strip of styrene to the back to support the joint. I used 60 grit sandpaper to roughen the surfaces to be glued then used a small paintbrush to apply a heavy coat of the glue to both surfaces.... gave it about a minute and then stuck them together.
Because my surfaces aren't perfectly flat I still needed to use clamps to hold the pieces in place for 24 hours until the glue fully cured. After an hour the initial curing was done but I gave it a full 24 to insure it was set.
Below are photos of the outside and inside... still messy and not at all cleaned up, but I wanted you to get an idea of what it looked like.
NOTE: After trimming down the two halves, I laid a full sheet of 150 grit sandpaper on a flat surface and ran the freshly cut edges of the pieces over it. This created a smooth flat joint that matched up with very little gap. Don't just rely on making a straight cut! Sand until it is perfectly straight so you have very little gap to fill later!